High-temperature, wear-resistant coating

ABSTRACT

A high-temperature, wear-resistant coated article, and a process for making it, comprising a substrate having a coated layer of metal oxide particles, such as Al2O3, substantially uniformly dispersed in a metal alloy matrix wherein said alloy comprises essentially at least one first metal selected from the group of iron, cobalt and nickel, and at least one second metal selected from the group of aluminum, silicon and chromium.

United States Patent [191 Wolfla [451 Feb. 4, 1975 HIGH-TEMPERATURE,WEAR-RESISTANT COATING [75] Inventor: Thomas A. Wolfla [73] Assignee: Union Carbide Corporation, New

York, NY.

[22] Filed: Nov. 17, 1972 [21] Appl. No.: 307,345

[52] US. Cl. 29/195, 117/71 M [51] Int. Cl B32b 15/00 [58] Field of Search 29/195 M; 117/71 M [56] References Cited UNITED STATES PATENTS 3,705,791 12/1972 Bredzs ..29/195M 3/1973 Levine 29/195 M 3/1973 Perugini 29/195 M X Primary Examiner-L. Dewayne Rutledge Assistant Examiner-E. L. Weise Attorney, Agent, or Firm-Dominic J. Terminello [57] ABSTRACT 3 Claims, No Drawings 1 HIGH-TEMPERATURE, WEAR-RESISTANT COATING FIELD OF THE INVENTION This invention relates to a high-temperature, wearresistant coated article, and a process for producing it, wherein the coated layer comprises metal oxide particles dispersed in a metal alloy matrix, said allo'y matrix comprising essentially at least one first metal selected from the group consisting of iron, cobalt and nickel and at least one second metal selected from the group consisting of aluminum, silicon and chromium, with the aggregate of the first metal being at least 40% by weight and the aggregate of the second metal being between about and about 40% by weight.

BACKGROUND OF THE INVENTION There are many excellent coatings available for pro viding a metal alloy substrate with a surface having specific characteristics suitable for a particular end use application. The coating'may be applied to increase the wear-resistant characteristics of the substrate, decrease the contact-friction characteristics of the substrate, electrically or thermally insulate the substrate, or protect it from oxidation or othercorrosive attack. For example, various types of coating materials can be ap plied on substrates by use of detonation guns, plasma are devices and the like, for improving the wear resistance of the substrates. However, only a few wearresistant coating materials can be used for hightemperature service, above 1000F, since the physical properties and/or coefficient of thermal expansion characteristics of most of the available coating materials are not compatible with the substrates used in hightemperature environments. Complex metal alloys containing tungsten, chromium or the like, are currently being used as wear-resistant coating materials for the surfaces of superalloy turbine blades. The composition of the coating is such that the coating will form carbide phases (WC, W C, CI'ggCs) during solidification. It is these hard refractory carbides that are primarily responsible for the wear resistance of the coated surfaces. However, at high temperatures in oxygen-containing environments, the hard refractory carbide surface is consumed by oxidation. Changing the alloy composition to increase corrosion resistance is not the solution since the change usually results in decreasing the wear resistance of the coating.

Another class of wear-resistant materials that is presently used is known as cermets, and includes materials consisting of a high volume fraction (usually greater than 80%) of hard particles such as oxides, or carbides and a metallic binder. Even though the metallic binder may be relatively corrosion resistant, these materials are unsatisfactory because they lack impact and fatigue resistance. Thus a problem plaguing the industry today is combining oxidation resistance and wear resistance in a useful coating.

The present invention overcomes the above drawbacks and limitations by being directed to a coating for a substrate whereby said coating comprises a relatively low volume fraction of metal oxide particles uniformly dispersed in an oxidation-resistant metal alloy matrix.

, SUMMARY OF THE lNVENTlON Broadly stated, this invention is directed to a hightemperature, wear-resistant coated article, and process for producing it, comprising a substrate with a coated layer, said layer composed of particles of at least one metal oxide substantially uniformly dispersed in a metal alloy matrix, said alloy matarix comprising essentially at least one first metal selected from the group consisting of iron, cobalt, and nickel, and at least one second metal selected from the group consisting of aluminum, silicon and chromium, and wherein the aggregate of the first metal is at least about 40% by weight of the alloy to provide sufficient strength and ductility and the aggregate of the second metal is between about 10% and about 40% by weight of the alloy to provide sufficient corrosion resistance.

The coating composition of this invention in a particulate form, can be deposited on a suitable solid structural substrate by conventional plasma-spraying techniques as disclosed in U.S. Pat. Nos. 2,858,4ll and 3,016,447, or by Detonation Gun techniques as disclosed in U.S. Pats. Nos. 2,714,563, 2,950,867 and 2,964,420 or by flame spraying techniques as disclosed in U.S. Pat. No. 2,861,900. The unique wear-resistant material so deposited will consist of a lamellar structure of interlocking and overlapping microscopic leaves me chanically bonded to each other and to said substrate without substantial alloying at the interface thereof, and be composed of metal oxide particles intentionally added to the oxidation-resistant metal matrix.

The metal oxide particles for use in this invention are selected from at least one of the group consisting of aluminum oxide, chromium oxide, beryllium oxide, titanium dioxide, silicon dioxide, thorium oxide, zirconium oxide, tantalum oxide, calcium oxide, magnesium oxide, hafnium oxide, yttrium oxide, the rare earth oxides and spinel combinations of the above such as MgO-Al O NiO-Al O and CoO'Al O The size of the metal oxide particlescan very between about 0.05 micron and about 74 microns, preferably between about 1 micron and 44 microns, and be present in a volume fraction of between about 2% and about 50%. preferably between about 5% and about 25%. Particle sizes below 0.05 micron are too small to add useful wear resistance, while sizes greater than 74 microns cause excessive wear of the mating surface. Volume fractions less than 2% do not provide sufficient wear resistance, but if the fraction is greater than 50%, the material has insufficient ductility, impact resistance and resistance to thermal fatigue. The particles, dispersed in the matrix as discrete components, must be stable in the intended high temperature operating atmosphere and substantially non-reactant with both the alloy of the matrix and the material of the substrate.

The metal alloy matrix of this invention comprises essentially at least one first metal selected from the group consisting of iron, cobalt and nickel, and at least one second metal selected from the group consisting of aluminum, silicon and chromium. The aggregate of the first metal should be at least 40% by weight and the aggregate of the second metal should be between about 10% and about 40% by weight. The balance of the metal alloy can be composed of one or more adventitious elements, and/or one or more elements or compounds added to impart mechanical strength and/or corrosion resistance at high temperatures; for example, tungsten, molybdenum, vanadium, manganese, carbon, rhenium, yttrium, lanthanum, boron, niobium, titanium, tantalum, zirconium and the like. The metal alloy should be of the particulate form and sized 200 Tyler mesh and finer so that it can be mixed with the metal oxide particles prior to deposition on a suitable substrate. The metal oxide particles and the components alloy powder; said alloy comprising essentially at least one first metal selected from the group consisting of iron, cobalt and nickel, and at least one second metal selected from the group consisting of aluminum, silicon of the metal alloy matrix material should be selected so and chromium, the aggregate of said first metal being that the metal oxide particles will not effectively react at least about 40% by weight and the aggregate of said with the alloy and thereby remain substantially dissecond metal being between about and about 40% persed in the alloy matrix as discrete stable particles. ln by weight; said metal oxide particles being sized beaddition, the final wear-resistant coating should have a tween about 0.05 micron and 74 microns and present Vickers Hardness Number (VHN) of greater than 500 10 in a volume fraction of between about 2% and about as determined in accordance with ASTM Test Method 50%; and wherein said alloy powder being sized about E92-67 using a 300 gram test load. Examples of admi- 200 Tyler mesh and finer; and rably suited alloys for the matrix Of this invention are I depositing said mixture of particles and powders Show" in Table onto a substrate by a technique selected from the group Some examples of substrate materials used in various i ti of detonation gun means, plasma spraying corrosive environments and admirably suited as submeans d fl Spraying means so as to dh i l strates for the coating Of this invention include, but are coat Said substrate a high-temperature wearnot limited Steel, Stainless Steel, iron base alloys resistant coating having a surface hardness of at least nickel, nickel base alloys, cobalt, cobalt base alloys, about 500 VHN chromium, chromium base alloys, refractory metals, EXAMPLE and refractory-metal base alloys. The specific coating composition selected for a substrate intended for a par- A base alloy F havmg the composltlon ticular end use environment should be selected so that shownm m n slzed Tyler mesh and finer it will adhere to the substrate without substantially was mfxed 3o'mlcron and Smaller Chromfum spalling or peeling while neither the metal oxide parti- Oxide Varlous Volume fractlons and deposlted cles nor the metal alloy matrix therein will effectively JT3D turbine blades using a detonation gun under react with the substrate in its intended environment. the conditions Outlined in Pats- 2,714,563 Any artisan can determine the choice of the coating 9 3 and 2,964,420 The blades were made of materials that can be adhesively deposited and which waspaloy, a nickel base superalloy Composed y will be compatible with a particular selected substrate Weight of 425 19-50 for a specified end-use environment. The deposited 0005 (1085 Zr, Mn Si coating shosuld consist of discrete metal oxide particles 0-030 5 math, CU C and balance dispersed substantially uniformly in the metal alloy ma- A 1/i1 X 1/1 inch Surface of t blade known s th trix in a size and quantity as recited above and have a notch was coated with the cobalt base alloy and chrosurface hardness of 500 VPN. The metal particles mium oxide mixture until a 0.008 to 0.010 inch thick should be stable in the alloy matrix and the overall layer was established. The coated blades were then high-temperature,wear-resistant coating should be statested in an engine simulator wear-test device that ble on the substrate in its intended end-use environcauses thermal stress and impact and sliding wear damment. Usually a coating of about 0.003 inch or thicker age similar to an actual engine by rubbing two blade Z- would be suitable for most applications. notch sections against each other. The temperature in As used herein, metal base alloy shall mean alloys the simulator during the test was recorded at ]650F wherein (899C). Due to the contact between the coated sur- TABLE I Total Total First Second Alloy Name Fe Ni Co Metal Al Cr Si Metal C Others Hastelloy x 18.5 47.3 1.5 67.3 22 0.5 22.5 0.10 0.5Mn, 0.6W, 9M0 Haynes 188 1.5 22 40.3 63.8 22 22 0.08 0.08La, 14w Udimet 700 0 53.3 18.5 71.8 4.25 15 19.25 0.15 0.038, 3.5Ti, 5.2Mo lnconel 718 18 53.5 71.5 0.6 19 19.6 0.04 5 Nb, 0.8Ti, 3 Mo Discaloy 55.8 26 81.8 0.10 13.5 13.6 0.04 0.0058, 1.75Ti, 2.75 Mo Coast Metal 64 3 5 40.6 48.6 28 1 29 0.85 1v, lMn, 19.5w

' Composition in weight percent.

the base metal is present in the largest proportion by faces of two blades, a wear scar was embedded in the weight. High temperature shall mean l00OF or higher. coated test surfaces. The depth of the wear scars in the Therefore substrates to be coated according to this invarious coating compositions tested is shown in Table vention should be such that they substantially maintain Ill. As demonstratively shown in the test data, the additheir integrity at high temperatures. tion of metal oxide particles, in various volume frac- The process of this invention entails the following tions, to the coating will substantially increase the wear steps: resistance of the coating without degrading its good oxa. preparing a mixture of at least one metal oxide seidation resistance. lected from a group consisting of aluminum oxide, chromium oxide, beryllium oxide, silicon dioxide, tita- TABLE H nium dioxide, thorium oxide, zirconium oxide, tantalum oxide, calcium oxide, magnesium oxide, niobium Compvsifion y Weigh! oxide, hafnium oxide, yttrium oxide, rare earth oxides, Cuba, Balance and spinel combinations of the above, with a metal Chromium 28 nickel, and at least one second metal selectaed from the group consisting of aluminum, silicon and chroby weigh mium, the aggregate of said first metal being at least 52%;? 2' 40% by weight of the alloy and the aggregate of said t I 3 5 second metal being between about and about 40% g ggg yp by weight of the alloy; the surface hardness of said Ma new 1 coated layer bein at least 500 VHN as determined 2 g using a 300 gram test load and the coated layer having aggregate of Gm metal in chains 48.65% a microstructure consisting of a thin lamel lar structure "aggregate of second metal in coating 29 a 10 of interlocking and overlapping microscopic leaves me- TABLE III Duration Material Depth of Wear of Test LlOl alloy 1 X 10' inch l2 hours LlOl alloy 6 v/o cl'gog less than l X 10 inch l2 hours LlOl alloy 4 W0 C503 4 X 10 inch 12 hours LlOl alloy 2 v/o C1203 2 X l0" inch 12 hours thorium oxide, zirconium oxide, tantalum oxide, siliconoxide, magnesium oxide, hafnium oxide, yttrium oxide, rare earth oxides, and the spinel combination of the above metal oxides, sized between about 0.05 micron and about 74 microns, and present in a volume fraction of between about 2% and about 50%; said metal alloy matrix comprising essentially at least one first metal selected from the group consisting of iron, cobalt and chanically bonded to each other and to said substrate.

2. The coated article of claim 1 wherein said substrate is selected from the group consisting of steel, stainless steel, iron base alloys, cobalt, cobalt base alloys, nickel, nickel base alloys, chromium, chromium base alloys, refractory metals and refractory-metal base alloys.

3. The coated article of claim 2 wherein said metal oxide particles are selected from a group consisting of aluminum oxide, stabilized zirconium oxide and chromium oxide; said metal alloy is selected from a group consisting of nickel base alloys, iron base alloys and cobalt base alloys, and said substrate is selected from a group consisting of nickel base alloys, cobalt base alloys and iron base alloys. 

2. The coated article of claim 1 wherein said substrate is selected from the group consisting of steel, stainless steel, iron base alloys, cobalt, cobalt base alloys, nickel, nickel base alloys, chromium, chromium base alloys, refractory metals and refractory-metal base alloys.
 3. The coated article of claim 2 wherein said metal oxide particles are selected from a group consisting of aluminum oxide, stabilized zirconium oxide and chromium oxide; said metal alloy is selected from a group consisting of nickel base alloys, iron base alloys and cobalt base alloys, and said substrate is selected from a group consisting of nickel base alloys, cobalt base alloys and iron base alloys. 